Extreme events rise with temperatures

A longer growing season may come with more regular droughts and heat waves, says researcher

The jet stream and storm paths are becoming loopier and lazier, resulting in more extreme weather over the Prairies and Great Plains as the planet warms.

Despite having what felt like colder winters and summers in the past few years, Western Canada is warming.

The region’s frost free days have jumped by about a month since the 1960s, while days above 35 C have doubled and those below -40 C have fallen to almost nothing from a half dozen.

Elaine Wheaton, a University of Saskatchewan researcher, says the trend to increased temperatures is long term.

The data shows a warmer prairie landscape, with nearly annual rises in average seasonal temperatures.

“Summer has seen some dramatic changes to the 1960s. Frost free in the early 1960s lasted 105 to 110 days. We have hit 140 and better in recent years,” she told a recent Saskatchewan Institute of Agrologists meeting.

“Plants and animals are having to adjust to these trends,” she said.

Aspen poplar now blooms a month earlier, which is a problem for fruit growers because bushes and trees that bud early can freeze when temperatures get colder again.

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As well, culex tarsalis mosquitoes and ticks get going earlier.

“We are starting to see pest species that were once limited to warmer regions in the U.S. showing up on the Prairies,” said Wheaton.

Changing jet stream and storm stream patterns are also resulting in more weather extremes.

Temperatures from 1948-2013 show an overall increase. Snow cover that was 12 centimetres in March in the 1960s is now nearly zero.

“Precipitation is less predictable than it used to be,” Wheaton said.

“Plant hardiness zone changes are at least one half zone change, and most of the Canadian changes are in 2, 3 and 4. In Saskatchewan, there is a lot more 3 and 4a and 4b.… Using the North American Drought Monitor, we can see an extreme drought in California reaching up to North Dakota and Minnesota and southern Manitoba, so there is real drought near by.”

She said a strong, later season El Nino condition currently exists, which might translate into a warm, dry summer on the Prairies.

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Wheaton said the type of droughts now seen in the United States can also happen on the Prairies, and farmers shouldn’t rule out severe droughts occurring without much warning.

“We are likely to see accelerated changes in above average conditions, milder winter, decreased snow cover, increased heat waves. Past droughts may seem mild compared with future droughts,” she said.

“Increased potential for major rainstorms and floods is a reality.… The 2002 drought reached places like Meadow Lake and northeastern Alberta, and grasslands were badly injured. It wasn’t that long ago.”

However, there might be an upside.

Longer warm seasons and greater heat units will allow more crop yields and biomass to be produced on the Prairies and Plains in the next 10 years, which will result in more cropping options and greater profitability.

“Farmers need to spend more time and resources monitoring the weather and planning for problems,” Wheaton said.

“Enhanced knowledge of opportunities and of issues such as insects, diseases and weeds will be important to producers.”

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Contact michael.raine@producer.com